[api-minor] Add basic support for the SetOCGState action (issue 15372)

Note that this patch implements the `SetOCGState`-handling in `PDFLinkService`, rather than as a new method in `OptionalContentConfig`[1], since this action is nothing but a series of `setVisibility`-calls and that it seems quite uncommon in real-world PDF documents.

The new functionality also required some tweaks in the `PDFLayerViewer`, to ensure that the `layersView` in the sidebar is updated correctly when the optional-content visibility changes from "outside" of `PDFLayerViewer`.

---
[1] We can obviously move this code into `OptionalContentConfig` instead, if deemed necessary, but for an initial implementation I figured that doing it this way might be acceptable.

web/pdf_link_service.js

@@ -493,6 +493,48 @@ class PDFLinkService {
     });
   }
 
+  /**
+   * @param {Object} action
+   */
+  async executeSetOCGState(action) {
+    const pdfDocument = this.pdfDocument;
+    const optionalContentConfig = await this.pdfViewer
+      .optionalContentConfigPromise;
+
+    if (pdfDocument !== this.pdfDocument) {
+      return; // The document was closed while the optional content resolved.
+    }
+    let operator;
+
+    for (const elem of action.state) {
+      switch (elem) {
+        case "ON":
+        case "OFF":
+        case "Toggle":
+          operator = elem;
+          continue;
+      }
+      switch (operator) {
+        case "ON":
+          optionalContentConfig.setVisibility(elem, true);
+          break;
+        case "OFF":
+          optionalContentConfig.setVisibility(elem, false);
+          break;
+        case "Toggle":
+          const group = optionalContentConfig.getGroup(elem);
+          if (group) {
+            optionalContentConfig.setVisibility(elem, !group.visible);
+          }
+          break;
+      }
+    }
+
+    this.pdfViewer.optionalContentConfigPromise = Promise.resolve(
+      optionalContentConfig
+    );
+  }
+
   /**
    * @param {number} pageNum - page number.
    * @param {Object} pageRef - reference to the page.
@@ -676,6 +718,11 @@ class SimpleLinkService {
    */
   executeNamedAction(action) {}
 
+  /**
+   * @param {Object} action
+   */
+  executeSetOCGState(action) {}
+
   /**
    * @param {number} pageNum - page number.
    * @param {Object} pageRef - reference to the page.